Apparatus for reduction of metallic material



Nov. 20, 1945.

H. A. BRASSERT ETAL APPARATUS FOR REDUCTION OF METALLIC MATERIAL4 FiledApril 6, 1943 4 Sheets-SheerI l Nov. 20, 1945. H. A. BRAssERT ET Ax.2,389,133

APPARATUS FOR REDUCTION oF METALLIC MATERIAL Filed April 6, 1945 4Sheets-Sheet 2 Nov. Z0, 1945. H. A. BRAssERT ET AL 2,389,133

APPARATUS FOR REDUCTION OFMETALLIC MATERIAL Filed April 6, 1945 4Sheets-Sheet 3 1/ /ll l/ Nov. 20, 1945. H. A. BAssERT ETAL 2,389,133

APPARATUS FOR REDUCTION OF METALLIC MATERIAL Filed April 6, 1943 4Sheets-Sheet 4 Patented Nov. 20, 1945 i 2,389,133 APPARATUS FORREDUCTION F METALLIC MATERIAL Herman A. Brassert, Washington, andCharles F.

Ramseyer, 01d Greenwich, Conn., assignorl to H. A. Brassert & Company,New York, N. Y.. a

corporation of Illinois Application April 6, 1943. Serial No. 481,968

4 Claims.

This invention relates to the production of metals and has particularreference to methods and apparatus for effecting reduction of finely#divided metallic ores or other oxides or sulphides, such as iron ore,pyriteS, mill scale, and other ferjetting eect tending to causechanneling. The hearth ls arranged horizontally and is preferably madeof heat-resistant metal for lightness and strength. The gas aperturesare preferably arranged vertically and the gas travels perpendicurousoxides, although the invention is not limited 5 larly or normally to thegeneral direction of to ferrous metals, but may also be used forpromovement oi the bed and, notwithstanding its duing non-ferrousmetals. high emergence velocity, is effectively distributed It is knownthat finely-divided solid behaves uniformly over the hearth surface by acap placed as a iiuid, and particularly so when continuously over eachaperture so that the gas is diffused unaerated. 'I'his phenomenon hasbeen utilized in der the edges of thecaps and bubbles up throughreducing finely-divided ores or other oxides by the bed from theenclosed gas chamber coextenmeans of hot reducing gases caused to flowsive with th hearth which forms the upper surthrough a bed of the oreunder such conditions face of the gas chamber. that the bed assumes astate equivalent t fluid- The chamber/fis supplied with gas at properity, and accordingly ilows along the hearth from temperature andpressure toeflect the reduction the charging to the discharging pointwhile the and any number of such complete self-contained ore is beingreduced. This method is disclosed hearths maybe enclosed in ahouslng,preferably in application Serial No. 338,560, led June 3, one above theother,`althougi1 each hearth is in- 1940, by J. C. Hartley, and avariant thereofis dependent ofthe other. Gas may be fed indedisclosed inapplication Serial No. 422,930, led pendently to each oneoffthosehearths, and the December l5, 1941, by C. J. Westling. In each gas canbe fresh'` in each instance or partly or case the hot reducing gas ispercolated through wholly \\spe\nt gas, particularly in the upper thebed of ore from below, the hearth being prohearths The depths of the orebeds 'on the vided with perforations or similar apertures for hearthsacLthe reducing power of the gas and that purpose. its velocity,tri'perature and pressure can be so In utilizing prior perforatedhearths for reducvaried that the spent gas leaving each hearth ing tineores, the gas is supplied at sufficient volmay be as close toequilibrium as possible, thus ume to effect reduction and ows throughthe realizing the optimum reducing power of the ore bed at suillcientvelocity to obtain the desired gases. A relatively thin bed of the freshore at fluid condition, but frequently channeling takes the top of thefurnace will have the same effect place, owing to temporary clogging ofsome of the on the reducing gases as a much thicker bed of hearthapertures, or because the bed happens to almost completely reduced orenear the bottom. be thinner at one point than another. Chan- Enclosing aplurality of hearths in a. single neling and consequent bursting oflarge gas bubhousing not only saves space and heat, but also bles at thesurface of the bed results in dusting, enables feeding of the materialfrom one hearth uneven ilow, and non-uniform reduction. to another forprogressive reduction in a manner We have found that the number of thegas apsimilar to the Herreshoi furnace, although rabertures may beincreased and the size of the gas bling arms and a 00I1t1`01 Shaft arenot required apertures through the hearth may be reduced since thematerial ows from the charging to the still further so that there is notendency toward discharging end of the hearth in the manner ofchanneling, and that an adequate tisupply of gas a fluid while beingreduced. Also the entire refor effecting complete reduction may beneverducing Operation may be maintained under sutheless supplied bymaintaining a relatively high DeI'ai'fmOSpheriC pressure i0 DI'OmOtereduction, gas pressure at the upstream ends of the aper- Since theSupply 0f reducing gas iS more Concentures without any undue disturbancein the bed. trated under these conditions and pressure speeds We employa hollow hearth containing between 11D the reactionits upper and lowerdecks e, volume of 'reducing In a preferred form of furnace embodyingthe gas under suilicient pressure so that the amounts Present invention,the elongated hearth may be of gas flowing through each aperture aresubspirally arranged so as to further conserve space stantially the sameor remain in constant reand heat, and this may be Conveniently done bylationship one to the other. An adequate volproviding a Circularplate-like hearth with a ume of gas may be supplied to the gas chamberspiral partition to which the material may be for effecting reductionand the desired fluidity, fed, either at the center or at the periphery,and even in very deep beds, without any concomitant when such hearthsare arranged one above the other the material is supplied alternately atthe center and periphery of the successive hearths.

For a more complete understanding of the invention, reference may be hadto the accompanying drawings, in which:

Figure 1 is a longitudinal section as seen along the line I-I of Fig. 2through the straight form of reducing furnace embodying the improvementsand utilizing the process of the present invention;

Fig. 2 is a horizontal section therethrough as seen along the line 2-2of Fig. 1, and illustrates the arrangement of the hearth surface;

Fig. 3 is a transverse section therethrough as seen along the line 3-3of Fig. 2;

Fig. 4 is an enlarged Vsection through the hearth as seen along the line4-4 of Fig. 1 and illustrates the construction of one of the bubblecaps;

Fig. 5 is an enlarged plan view of one of the bubble caps; 1`

Fig. 6 is a vertical section through the preferred circular forni ofreducing furnace, as seen along the line 6-6 of Fig. '1;

Fig. '1 is a horizontal section therethrough as seen along the line 1-1of Fig. 6 and illustrates the` arrangement of the first or upper hearth;and

Fig. 8 is a horizontal section at 8 3 of Fig. 6 and illustrates thesecond hearth.

Referring to Figs. 1,` 2 and 3 of the drawings, the furnace I comprisesa rectangular housing preferably formed of welded 4% to 6% chrome steelor other suitable heat-resistant metal provided with a double bottomformed by a horizontal upper deck I I spaced above the lower deck orbottom I2 so as to form a sealed chamber into which a reducing gassupply pipe I3 leads. The upper deck II forms the horizontal hearth ofthe furnace and is perforated, the perforations being spacedfrom two tosix inches apart and each containing a plug I4 shown in Fig. 4,preferably threaded into the perforation in the hearth II as shown, orit may be force-fitted therein. Each plug I4 is provided with arelatively small central orifice I5, for example, of 1A; to V4 inchdiameter, or of a suitable diameter determined by capacity for theparticular furnace to be employed. A. plate I6'is securedas by weldingto the upper end of the plug I4. This plate is provided with atransverse slot I1 shown particularly in Fig. 5, and the upper end oftheplug I4 is provided with a transverse notch I8. Gas emerging from theupper end of the orice I impinges against plate I6 and traverses notchI8 and slot I1 so that the gas ows beneath the edge of the plate I6,which is preferably also spaced abovev the upper surface of hearth II bymeans of integral studs I9. The whole plug and cap-plate organizationI4-I6 just described may be conveniently termed a bubble-cap, and isdesignated 20. Accordingly, the entire hearth II is studded withbubble-caps 20 supplying gas from the gas chain-y ber 2| beneath thehearth II.

The upper surface of hearth II is subdivided by several parallelvertical partitions 22, 23 and 24. Partition 22 extends from thelefthand end of the hearth II, as shown in Fig. 2, but stops short ofthe righthand end thereof, so as to leave an end passage 25. The centerpartition 23 extends from the righthand end of the hearth II but stopsshort of the lefthand end thereof, leaving an end passage 26. Partition24, like partition 22, extends from the lefthand end of the hearth IIbut stops short of the righthand endthereof, leaving the passage 21.

It will be observed that these partitions provide a zig-zag channel ofsubstantial length within a small space, equivalent to a longtunnel-like furnace. The effective hearth begins with the channel 28between partition 22 and the side wall 29 of the furnace leading throughend passage 25 to channel passage 30 between partitions 22 and 23,leading through end passage 26- to channel 3I between partitions 23 and24, leading through end passage 21 to channel 32.between partition 24and side wall 33. It will be understood that this zig-zag channel issupplied through its entire extent by reducing gas from gas chamber 2Ithrough the bubble-caps 20. As shown particulariy in Figs. 1 and 3, thepartitions 22, 23 and 24 stop short of the top 40 of the furnace and maybe welded or otherwise secured to the upper surface of hearth I I.

Discharging into the closed end of channel 28 at the lefthand uppercorner of Fig. 2 is the supply pipe 34 for charging the furnace Il) withthe finely-divided oxides to be reduced. Pipe 34 ls preferably welded tothe top 40 of the furnace I0 and its lower end is threaded and carriesan advinstable collar 35. By screwing collar 35 upadjusted. Collars 31screw into each other as shown and may be increased or decreased innumber to obtain the desired depth of bed at discharge, winch is alwayslower than the depth of the bed at the feeding end, so that a head ofthe material is maintained in order that it may flow in the manner to bedescribed. The discharge pipe 36 may lead directly to a briquettingmachine, not shown, for compacting the reduced material into'briquetteswhile still hot from the reducing operation and while still in areducing atmosphere, in the manner described in Patent No. 2,287,663,issued June 23, 1942, to H. A. Brassert. If desired, the reducedmaterial may be further concentrated before briquetting, also asdescribed in said patent.

Leading from the upper end of the furnace I0 is a spent gas dischargepipe 38 which may conduct the gas to a reforming or recovering plant foreffecting reuse of the gas. A perforated plate 38 is preferablysuspended in spaced relation to the top 40 of the furnace, so that thespent reducing gas diffuses uniformly therethrough and its velocityretarded so that it does not carry out of the furnace any substantialamount of nes that may result from dusting.

An access door 4I preferably tted with a peep tube 42 is provided in thelefthand end 43' of the furnace I0, and a similar peep tube 44 may beprovided at the righthand end 45 of the furnace I 0.

In operation, in accordance with the process of this invention, thefurnace I0 is supplied with iron ore or other oxide through supply pipe34, the material being previously ground to 20 to 150 mesh andconcentrated to substantially remove the gangue according to knownmethods. The depth of the bed at the discharge end is deterthe deck IIis always less than the height of the lower end of the collar 35 abovethe deck II, so that a head of the finely-divided material is maintainedat the feed end, the differential depending upon depth of bed desired,iineness of the ore, nature of reducing gas, temperature, etc.

The reducing gas, preferably pre-heated to have a temperature in the bedof from 1100 to 1500 F., is supplied by pipe I3 to the chamber 2|, belowthe hearth I I, and at a pressure of say thirty pounds per square inchabove the internal furnace pressure. At this temperature the gas read--ily reduces the oxide but is not high enough to cause the particles toagglomerate and frit together, so that they remain separate and distinctthroughout the operation and hence retain the fluid-like flow whenpermeated by the gas in the manner to be described.

The gas accordingly flows at substantial velocity through the orifice I5of each bubble-cap 20' and impinges against the cap plate I6 thereof soas to be diused below its edge into the finely-divided material on thedeck I I. Under these conditions, the volume and velocity of gas flowinginto the bed from each bubble-cap 20 is substantially the same, so thatthe action of the gas throughout the bed is uniform. The gas is suppliedin adequate volume to effect reduction at the temperature given and toproduce the desired fluidity described, and usually, particularly whererelatively deep beds are employed, the amount of gas necessary to obtainthe desired fluidity of the bed is in excess of that theoreticallynecessary to deoxidize the ore. Accordingly a surplus of reducing gas issupplied which may be recovered and recirculated. For example, ifhydrogen is used, the water vapor resulting from the reaction may bewashed out to leave hydrogen for recirculation. Similarly where carbonmonoxide is used, the resulting carbon dioxide may be washed out withalkaline water and when mixtures of hydrogen and carbon monoxide areused the washing treatment removes both the water vapor and carbondioxide. Other recovering means for purifying the unused oxidizing gasmay be used so that it may be recirculated. Although at the beginning ofthe operation, all of the finely-divided material is located only at thefeed end of the zig-zag hearth channel under feed pipe 34, the fluidityimparted thereto by the gas causes it to rapidly flow along the hearthII between the partitions and to level out until it begins to ilow outof the discharge pipe 36.

It will be observed that the general direction of flow of the gasissuing from bubble-caps 20 is perpendicular or normal to the generaldirection of movement of the bed on the horizontal hearth II, and thisaction coupled with the even distribution of the gas over the entiresurface of the hearth II` without jetting results in an even, steadyflow of the material along the hearth without formation of large gasbubbles or channeling and consequently there is little or no clusting.The entire bed is accordingly in a fluidlike state and each particle issuspended in the gas which reduces it while maintaining it so suspended,the spent reducing gas rising to the top 'of the bed and beingimmediately replaced by fresh reducing gas entering the bed from belowso that reduction is rapid and continuous, augmented by the rubbingbetween the particles in the bed, which aids in removing the spentreducing gas which tends to cling to the surface thereof. The spentreducing gas is immediately f -removed through pipe 38.

The furnace I0 is preferably so constructed that two or more may bestacked in vertical relation whereby the reduction is progressive in adownward direction, beginning with partial reduction in the upper one,which discharges into the next lower section, which continues reductionand in turn discharges into the one below, and so on until completereduction is obtained. In this way the throughput on a furnace may beincreased materially over the use of one furnace alone, although it isto be understood that by proper control one furnace unit II) will effectthe complete reduction, but at a slower rate.

When several furnace units I0 are so superimposed, it will be observedthat in each unit fresh gas is supplied to the materialv from the hollowhearth. so that reduction is expedited and more eflicient operation isobtained, although,

if desired, the partially spent reducing gas, containing an excess ofunoxidized gas, may be delivered from the lowest hearth to the upperhearth, and the like, since only partial reduction 'is effected on thetop hearth. Whether one or more units I0 are so used, the furnace ispreferably jacketed with insulating material or mounted in an insulatingenclosure to conserve heat, which is also conserved when two or moreunits are mounted together, since heat is transmitted from one unit toanother. Heat may also be conserved by partially pre-heating the freshreducing gas in a heat-exchanger by means of the sensible heat in thespent reducing gas withdrawn by pipe 38. By withdrawing the spentreducing gas from' 38.by means of a suction pump, the interior of thefurnace Ill 'may be maintained under a slight vacuum to expedite thepurging of the spent reducing gas, although as will be described, it ispreferred that the furnace be maintained under pressure 'to expedite thereducing action.

Instead of employing straight hearth channels in the manner described,they may be arranged spirally, as shown in Figs. 6, 7 and 8. Referringto Fig. 6,y the furnace preferably comprises a cylindrical housing 45 ofsteel or other suitable heatresistant metal, enclosed in suitable heatinsulation 46 and capable of withstanding internal superatmosphericpressures on the order of 15 to 30 pounds per square inch gage. Theupper portion of the housing is provided with a centrally located doublebell and hopper arrangement 41 including the separately-operated upperfeed bell 48 and lower sealing bell 49. This arrangement serves as apressure lock, enabling feeding of the finely-divided metallic oxide tobe reduced into the housing 45 without losing pressure during theopening of the feed bell 48.

Located within the housing 45 and positioned one above the other is aseries of independent, self-contained hearths, four of which are shownin Fig. 6, but more or less may be used, depending upon requirements. Asbefore, each hearth is preferably composed of heat-resistant metal. Theupper unit 50 comprises a hearth deck 5I extending across the housingand having spaced peripheral spent gas slots 52 and one peripheraldischarge slot 53 for .the material under treatment. The hearth 5I has agas chamber 55 beneath it and this slot 53 having a dam 54 extendingacross its mouth.

The hearth deck 5I is studded with bubble-caps 28 illustrated in Figs. 4and 5, and as described in connection with Figs. 1, 2 and 3, they supplydiffused reducing gas into the nely-divided material constituting thecharge on each hearth.

Secured on the upper surface of the top hearth 5I is a spiral partition51 of heat-resisting steel. The length of the spiral partition 51 fromthe center, to which the material is dischargedfrom the doub1e beu andhopper fee 41, to the discharge passage 53 at the periphery, dependsupon the volume of material to be treated and the rate of its travelnecessary to secure the desired reduction. For instance, for atwenty-foot inside diameter hearth the total ore travel from feed todischarge should be, under normal oper `ting conditions, equal to about188 feet, and ac rdingly the length of the spiral partition 51 must besuch to provide a length of travel of that distance.

The third hearth from the top, designated 58, is identical to the` tophearth 50, but the second hearth from the top, designated 59, and thelower hearth, designated 60, are constructed differently from hearths 50and 58, and have cente discharge passages 6| and 62, respectively,instead of peripheral discharges, since these two decks receive thematerial from the corresponding upper decks at their periphery, fortravel spirally inwardly to the center. The second and lower hearths, 59and 60, are identical, and description of one of them, 59, will suilce,and is illustrated in Fig. 8. The top of hearth deck 64 is fitted with aspiral partition 65 leading from the periphery at 66 to the centerdischarge opening 6l lled with the dam 61. Also, like upper hearth 50,the second hearth 59 is provided with an enclosed bottom gas chamber 69,as is like lower hearth 60.

Thus, the material discharged from upper hearth 50 falls on theperiphery 66 of the next hearth 59, travels spirally inwardly for adistance determined by the length of the spiral partition 65, anddischarges at the center through passage 6l upon the center of the nexthearth 58. On deck hearth 58 the material travels outwardly from thecenter to discharge through peripheral passage 68 to the lower hearth 60on which it travels inwardly to discharge centrally at 62. Since thepartitions of all hearths 59, 59, 58 and 60 are spiral in shape, theaggregate length of their convolutions determines length of the furnace.For example, in the furnace illustrated, each hearth is designed to havethe same length and accordingly travel of the material on ea'ch deck isapproximately 188 feet,

making a total hearth length of about '150 feet for the four hearths.

The lower or discharge end of the furnace housing 45 converges into adischarge cone 10 feeding to a pair of driven briquetting rolls 1I and12, which are enclosed within a casing 13 fitted with a normally closedpressure valve or discharge hopper 14, this hopper 14 and thebriquetting rolls 1I and 12 constituting a fonn of gas pressure lock.

Located along one side of the furnace housing 45 is a manifold 15 forsupplying reducing gas by pipes 16 to each of the gas chambers 55 and 69of the several hearths 50, 59, 58 and 66. The flow of the reducing gasto each hearth may be regulated by means of a separate valve 11. 'I'hereducing gas, preferably cleaned and desulphurized if necessary, ispre-heated to such temperatures as to be delivered to the discharge endsof the orifices in the bubble caps 20 at a reducing the effectivehearth' temperature of between 1100 and 1500 F., below the'fusionpoint.v

Furnace 45 is pressure-sealed as described, at

the charging feed hopper 41 and at the discharge end, at the briquettingrolls 1l and 12 and discharge hopper 14. The spent gas discharge pip;`18 leading from the furnace 45 is preferably fitted with a pressureresponsive valve 19, set to the internal pressure desired for thefurnace 45, so that the internal pressure will remain substantiallyconstant at, say l5 to 30 pounds per square inch gage.

In operation, in accordance with the process of this invention, thefurnace 45 is supplied with iron ore or other oxide from hopper 41, thematerial being previously ground to 20 to 150 mesh and concentrated tosubstantially remove the gangue according to known methods. The reducinggas, preheated as described, is supplied from manifold 15 to the severalindependent gas chambers 55 and 5,9, within each double-deck hearth at apressure of say five pounds per square inch above the internal furnacepressure. Thus, if the internal furnace pressure is fifteen pounds persquare inch, the gas is then supplied to these gas chambers at twentypounds per square inch. The gas accordingly llows at substantialvelocity through the bubble-caps 20 for flow into the ma-` terial whichlies on the upper deck 5| of top hearth 50 within the spiral partition51.

The material discharged on the top deck 50 'by the feed bell 41 falls onthe center thereof, but owing to the fluidity imparted thereto by thegas percolating therethrough, the material rapidly level out, although ahigher level or head is malntained at the center than at the dam 54 atthe periphery of the spiral partition 51 as is indicated in Fig. 6.Because the gas emerging from beneath the bubble-caps 20 imparts theretoa condition equal to fluidity in the manner described, the headmaintained at the center of the spiral 51 causes the material to ow fromthe center around the spiral to discharge over dam 54 into passage 53 atthe periphery, meanwhile being reduced at least -to a certain extent.

The partially reduced material then falls to the next deck 59 at theperiphery thereof and again flows spirally around it within partition65, owing to the iiuid condition imparted thereto by the gas owingthereinto from the bubblecaps and the head maintained at the periphery,as indicated. However, in this instance the flow is inward from theperiphery to the center. The fresh reducing gas supplied to the hearth59 from the gas chamber 69', therein further reduces the material andwhen it dischargesover dam 61 intothe center passage 6| to the center ofthe hearth 58 below, it is largely reduced. Further reduction takesplace in the same way on hearth 58, by means of a fresh supply ofreducing gas supplied thereto, the material being received at the centerand rowing spirally outwardly to discharge over the dam into peripheralpassage upon the periphery of the last hearth 60. There the reduction iscompleted by means of the fresh supply of gas furnished to lower hearth60.

The completely reduced material discharged from the center opening 62 ofthe last hearth 60 into the cone 10 is fed by gravity to the briquettingrolls 1| and 12, which immediately compact it while still hot from thereducing operation into self-sustaining briquettes before the materialhas any opportunity for contamination, the briquetting operation beingconducted in the reducing atmosphere, as described in said PatentAcamaras No. 2,287,663. The completed briquettes collect within thehopper 40 and may be periodically removed. l

The spent reducing gas is effectively purged from the surfaces of theparticles by friction and attrition as the particles fall freely fromone hearth to another, so that by the time they reach the hearth belowtheir surfaces are substantially freed of spent reducing gas, and freshgas may readily attack the unreduced portions. Also, as previouslydescribed, the particles rub against each other in the bed and the spentreducing gas is in that fashion further purged from the bed and iscarried out Iby the fresh reducing gas. By maintaining the entirefurnace under internal superatmospheric pressure in the order of 15 to30 pounds gage, the reducing gas is supplied in more concentrated formto the particles and thus reduction is promoted. The straight typefurnace shown in Figs. 1 to 3 may also be placed under pressure in thesame way, if desired.

The spent reducing gas passes from each hearth through openings 52 atthe periphery of each hearth into the annular space 80 for exit throughthe gas discharge pipe 18 for recovery and recirculation of theunoxidized reducing components thereof in the manner described.

It will be seen that the method and apparatus of this invention enablesfresh reducing gas to be supplied to any number of hearths to carry on aprogressive reduction of metallic oxides in an economical and efficientfashion. Because the gas orifices are small, although numerous,v and thegas is diffused from a relatively large reservoir of gas underrelatively high pressure, the tendency to channeling and consequentdusting and irregular iiow and reduction is avoided. Also, the spent gasis removed from each hearth as it is discharged from the material beingtreated, and is not re-used without reformation and cleaning, but,instead, a supply of fresh reducing gas is used for that purpose. Thedepth of the ore beds on the hearths are adjusted by raising andlowering the discharge dams, and the reducing power of the gas and itsvelocity, temperature and pressure can be so varied that the spent gasleaving each hearth is as close to equilibrium as possible. Thus, thefresh ore on the upper hearth in Fig. 6 deoxidizes the gas to a greaterdegree than the nearly completely reduced material on the lower hearthand, therefore, a thinner -bed on the upper hearth is preferred so thatthe gas emerging therefrom is no more deoxidized than that emerging fromthe lowest hearth, with progressively greater depths and proportionateresults from the intermediate hearths. Furthermore, in the two types offurnace described the temperatures and pressures may be maintained, andadjusted if desired, in accordance with operating requirements. so as toobtain most efllcient and complete reduction within a small space andwith a minimum of parts to the exclusion of any moving parts exceptthose used for Ibrlquetting purposes.

Although the invention has been illustrated and described in connectionwith straight and circular furnaces, it may also be constructed in otherforms with one or more decks as desired. and other changes in the methodand apparatus of this invention may be made within the scope of theappended claims.

We claim: y

l. In apparatus for reducing iinelydivided metallic material, thecombination of a housing, a horizontal hearth therein having amultiplicity `material without propelling -said material along saidhearth and to prevent said material from entering said apertures bygravity, means extending into said housing and disposed adjacent one endof said hearth for feeding said finely-divided material upon the hearthfor reduction by the gas emerging from said apertures, and means in saidhousing for discharging said reduced material from said hearth, saiddischarging means having an outlet at a lower level than the llevel ofthe material at said one end of the hearth whereby said fluidizedmaterial moves along said hearth by gravity flow.

2. In apparatus for reducing finely divided metallic material, thecombination of a housing, an elongated horizontal hearth therein havinga multiplicity of substantially uniformly distributed aperturestherethrough, said apertures being less than one-quarter inch indiameter, a casing forming a gas chamber beneath said hearthcommunicating with said apertures, a pipe leading from the exterior ofsaid housing into said chamber for supplying preheated gas underpressure thereto, means on said hearth overlying said apertures fordiverting the gas issuing from said apertures laterally in alldirections to fiuidize said material without propelling said materialalong said hearth and for preventing said material from entering saidapertures by gravity, a plurality of spaced partitions extendingalternately in opposite directions part way across said hearth to forman elongated relatively narrow zig-zag path for movement of the materialalong said hearth, means extending into said housing and disposedadjacent one end of said hearth for feeding said finely-divided materialto the hearth for reduction by the gas emerging from said apertures, andmeans in said housing for discharging said reduced material from saidhearth, said discharging means having an outlet at a lower level thanthe level of the material at said one end of the hearth whereby saidfluidized material moves along said hearth by gravity flow.

3. In apparatus for reducing nely-divided me-V tallic material, thecombination of a substantially circular horizontal hearth having amultiplicity of substantially uniformly distributed, spaced,pressure-reducing gas apertures therethrough, said apertures notexceeding one-quarter inch in diameter and being of substantiallyuniform size, a casing forming a gas chamber beneath said hearthcommunicating with said apertures, a pipe connected to said chamber forsupplying preheated gas under pressure thereto, means on said hearthoverlying said apertures for diverting the gas issuing from saidapertures laterally in all directions to iluidize said material withoutpropelling said material along said hearth, and for preventing saidmaterial from entering said apertures by gravity, a spiral partition onAthe upper surface of said hearth providing an elongated relativelynarrow path for the material, means for feeding the finely-dividedmaterial upon the hearth at one end of the spiral for reduction by thegas emerging from the apertures in said hearth, and means in saidhousingfor discharging said reduced materiaHrom said hearth, said dischargingmeans having an outlet at a lower level than the level of the materialat said one end of the spiral whereby said iiuidized material movesalong said hearth by gravity iiow.

4. In apparatus for4 reducing ilnely-divided metallic material, thecombination of a housing, a plurality of substantially circularhorizontal hearths arranged in :spacedY superimposed relation in saidhousing, alspiral partition on each hearth providing an elongated narrowpath for movement of the material along said hearth, each hearth havingsubstantially uniformly distributed, spaced, tine pressure reducingapertures therein not exceeding one-quarter inch in diameter, means onsaid hearths overlying said apertures for preventing said material fromentering said apertures by gravity, a casing secured benesth each hearthforming therewith a gas chamber for supplying gas to said apertures,alternate hearths having a discharge passage at the periphery of thecorresponding spiral for discharging material by gravity to the hearthbelow, and the remaining hearths each having a discharge passage leadingto the hearth below from the center o! the corresponding spiral, meansextending into said housing for feeding the material to be reduced tothe uppermost hearth at the end of the spiral path opposite thedischarge passage, and means for supplying preheated reducing gas independently to said gas chambers o! the several heart-hs for emergenceat reduced pressure from the apertures thereof to diil'use through thematerial thereon to reduce the same.

HERMAN A. BRAssERT. CHARLES F. RAMsEYEa.

